The invention concerns a method for providing the tubular roll mantle of a roll in a paper machine or equivalent with glide bearings, in which method the roll mantle is supported on the stationary roll axle by means of hydraulic glide bearing elements acting upon the roll mantle or upon the roll ends, which glide bearing elements are loaded hydraulically by means of the pressure of a pressure medium, and which roll is loaded from outside radially at least in the direction of one plane, i.e. in the so-called principal loading direction, in which connection the roll mantle is supported on the roll axle by means of glide bearing elements acting radially in opposite directions substantially in the principal loading direction.
The invention also concerns a roll that is provided with glide bearings for a paper machine or equivalent and for carrying out the method, in which roll the roll mantle of the roll is supported revolvingly on the stationary roll axle by means of glide bearing elements acting upon the inner face of the roll mantle and/or upon the roll ends, which glide bearing elements are loaded by means of the pressure of a hydraulic pressure medium, and which roll is loaded from outside radially at least in the direction of one plane, i.e. in the so-called principal loading direction, in which connection the roll mantle is supported on the roll axle by means of glide bearing elements acting radially in opposite directions substantially in the principal loading direction.
In the prior art, tubular rolls of paper machines were commonly journalled from the ends of the roll mantle by means of roller contact bearings on the roll axle. Such a conventional mode of journalling has its advantages, among other things that the journalling can be accomplished quite simply, and so far its costs have been considered to be relatively reasonable. Such a conventional mode of journalling, in which the roll mantle is mounted on the axle stationarily from its ends, is, however, not suitable for even nearly all applications of use in paper machines. In quite a number of cases, the roll mantle must have a possibility to move radially in relation to the roll axle, which property is quite often required, for example, from variable-crown rolls and from rolls adjustable in zones which are in nip contact with a backup roll. Besides the fact that, in a variable-crown roll, attempts are made to shape the roll mantle in a controlled way by means of the crown variation devices in particular in view of regulation of the profile of linear load, the roll ends must also be able to move in the radial direction in relation to the axle in order that the profile of linear load could also be controlled in the end areas of the roll. Besides the properties of profile regulation in the end areas, the regulation of the loading in the end areas of the roll also affects the control of the temperatures in the end areas.
Owing to what has been stated above, rolls have also been developed in which the whole roll mantle can move radially in the direction of loading in relation to the roll axle. Among other things, in the applicant""s EP Patent No. 0,332,594 of earlier date, one such roll is described, in which the end bearings of the rolls have not been mounted directly on the central axle of the roll, but the bearings have been fitted on separate annular parts which can move radially in relation to the roll axle. The variable-crown roll in accordance with said EP patent is a nip roll, and the radial movement of the roll mantle is confined to the direction of the nip plane. The movement has been achieved so that hydraulic power units have been fitted between said annular parts and the roll axle, which power units shift the end bearings towards the nip or away from the nip by means of a hydraulic pressure medium. The principal object of said solution is opening and closing of the nip. There is also a great number of other rolls of similar type, which produce a substantially similar action while accomplished with a somewhat different technique.
The roller contact bearings in a roll produce quite considerable drawbacks and/or problems for the manufacture and operation of the roll. It is one substantial draw-back that roller contact bearings require machining of their own in the roll mantle.
Wear of the bearings may also result in problems, and roller contact bearings further impose their restrictions concerning the oil that can be used in the roll. It can be considered that a drawback of the conventional mode of journalling is at least the limitations of speed, because even now the speeds of rotation of rolls exceed the highest speeds permitted by bearing manufacturers, as well as the rolling accuracy, for, with the present technology, it is very difficult to improve the rolling accuracy of an assembled roll further. In a conventional roll, any defects are summed up in an assembled roll even if all the components, such as bearings, bearing housings, outer face of the mantle, etc. are machined as precisely as possible.
Journalling of the roll mantle with glide bearings is also known from the prior art. Such rolls with glide bearings are described, among other things, in the U.S. Pat. Nos. 5,060,357, and 5,111,563 and in the applicant""s published EP Patent Application No. 0,672,786 of earlier date. In the roll in accordance with the U.S. Pat. No. 5,060,357, the roll mantle is provided with roller contact bearings fitted in the areas of its end pieces, which bearings are fitted on separate annular parts similar to those used in the above EP Patent No. 0,332,594. The roll is meant to be a nip roll, and its roll mantle can move in the direction of the nip plane in relation to the axle, among other things, in view of opening and closing the nip. The support of the roll mantle in the lateral direction, i.e. in the direction transverse to the nip plane, has been arranged by means of quite a complicated construction of glide bearings, by whose means attempts are made to make the movement of the roll mantle take place exactly in the direction of the nip plane. It is a drawback of the construction described in said U.S. patent exactly that it is complicated, among other things, with a number of glide faces and linkage arrangements, for which reason the reliability in operation, the controllability, and the dependability of the construction cannot be considered to be very good. It is a further problem in the solution of U.S. Pat. No. 5,060,357 that, by means of the equipment, it is impossible to compensate for any forces of transverse direction applied to the roll from outside, since such forces result in failure of the oil film between the glide shoes and the inner face of the roll mantle.
In the U.S. Pat. No. 5,111,563, an arrangement of support of a roll with glide bearings in the lateral direction is described which is simpler than the solution of the U.S. patent mentioned above. In this solution, the journalling with glide bearings in the lateral direction has, however, been accomplished with a linkage arrangement which cannot compensate for lateral forces applied to the roll from outside either.
In the applicant""s earlier EP Patent Application (application publication No. 0,672,786), a number of alternative solutions for providing a roll with glide bearings are described, by means of which solutions a considerable improvement is provided over the U.S. patents mentioned earlier. Even though the operation of the roll described in the EP publication No. 0,672,786 has proved good and reliable, it has been a problem that the construction described in said EP publication is somewhat complicated, and it is desirable to simplify this construction so that the simplification of the construction also results in improvement of the reliability of operation. It is a particular objective to completely abandon the regulation device described in the EP publication, by means of which device the vertical movements, i.e. the movements of the roll mantle in the principal loading direction, in particular in the direction of the nip plane, are controlled. In particular in solutions in which said roll is used as a roll of a supercalender, in certain situations it is somewhat problematic to be able to keep the roll in the desired state and position even if the hydraulic system had been switched off completely. It is in particular desirable also to provide an improvement for such a solution.
The object of the present invention is to provide a novel method for providing the tubular roll mantle of a roll of a paper machine or equivalent with glide bearings as well as to provide a roll fitted with guide bearings by whose means drawbacks involved in the prior art are avoided, and by means of which method and roll, at the same time, a substantial improvement is achieved over existing constructions and methods.
In view of achieving the objectives of the invention, the method in accordance with the invention is mainly characterized in that, to the glide bearing elements acting in the principal loading direction in opposite directions, the loading pressure and the lubricant are fed as separated from one another so that, when the roll mantle is allowed to be displaced over a certain distance in the principal loading direction, the movement of the roll mantle, the speed of movement, and the change in the speed are regulated by opening, closing, and/or throttling the flow in the pressure duct of the loading pressure, in which connection the lubricant can be fed without interruption with the desired pressure and flow rate to the glide bearing elements irrespective of the loading pressure and of the position of the roll mantle.
On the other hand, the roll in accordance with the invention provided with glide bearings is mainly characterized in that the feed of the hydraulic loading pressure to the glide bearing elements acting in opposite directions in the principal loading direction is substantially completely separated from the supply of lubricant passing to said glide bearing elements, so that, for the feed of the loading pressure, there is a pressure duct of its own, and for the feed of the lubricant there is a separate lubricant duct, in which connection a certain maximal movement of shifting is permitted for the roll mantle in the principal loading direction, and said movement of the roll mantle, the speed of movement, and the change in the speed have been arranged to be regulated by opening, closing, and/or throttling the flow in the pressure duct of said loading pressure, and in which connection the lubricant can be fed with the desired pressure and flow rate to the glide bearing elements irrespective of the loading pressure and of the position of the roll mantle.
By means of the present invention, a number of remarkable advantages are achieved over the prior art, and of these advantages, among other things, the following should be mentioned in this connection. First, in the solution in accordance with the present invention, the mode of journalling is considerably simpler than in the prior art, for no separate regulation device for controlling the movements of the roll mantle is needed in the solution of the present invention. In the invention, the journalling, of the roll mantle with slide bearings has been accomplished so that the roll mantle can be locked in the desired position even if the hydraulic system had been switched off. Further, in the present invention, the quantity of lubricant passing through the glide bearing elements can be regulated, and thus, the oil flow passing through the elements can be used, for example, for cooling the end areas of the roll or for any other regulation of temperature. Further, as was already stated above, the mode of carrying out the invention is very simple and, consequently, reliable in operation. The further advantages and characteristic features of the invention will come out from the following detailed description of the invention.